WASHINGTON (AP)  Could eating a mere 100 fewer calories a day improve Americans' health by fighting the weight creep that adds up to, on average, 2 pounds a year?

Cutting out a cookie or taking fewer bites of a hamburger each day could help with weight later.

By Vinny Tennis, AP

That's the argument of a well-known obesity researcher. A few pounds each year eventually means big trouble, says Dr. James Hill of the University of Colorado. He says fending off those pounds simply by cutting back on a cookie or taking three fewer bites of a fast-food hamburger each day may be easier than losing weight later.

Hill acknowledges he has not proved yet that such a simple step works.

But scientists are searching for different approaches to what is fast becoming a national epidemic. Sixty percent of U.S. adults are overweight, and the government blames 300,000 deaths a year on weight-related diseases.

"The biggest problem we face in America is not terrorism. The biggest health problem we're facing is obesity," Dr. Julie Gerberding, head of the Centers for Disease Control and Prevention, told The Associated Press last week.

Fixing the problem will require changing societal norms starting with children, she said, such as doing more and eating less in a society that encourages more driving than walking and provides unfettered access to calorie-laden foods.

To focus attention on the problem, the journal Science, in Friday's edition, turned to obesity researchers for opinions on what it will take to lower the scales.

Hill's response was to examine government figures showing about 40 million adults are obese and documenting Americans' steady weight gain in recent years.

"The future is not hopeful unless we act now," he concluded. If current trends continue, he estimated that 39% of adults will be obese by 2008, compared with 31% in 2000.

Losing weight and keeping it off can be hard. So Hill and colleagues calculated what he calls the energy gap — how many calories are consumed but not burned off.

Using that same government data, he estimated that, on average, people gain 2 pounds a year, which equals 50 extra calories stored each day. Because the body can store half of calories consumed, he said preventing that 2-pound weight gain might simply require eating 100 fewer calories a day.

There are problems with that simple approach, says Dr. Jeffrey Friedman of Rockefeller University, who discovered the obesity hormone leptin in 1995. Some people gain 10 pounds in a year while others gain none. Also, few people actually know how many calories they consume.

"We don't simply need to reiterate the old nostrums. We need to develop a fuller understanding of how to deal with" obesity, he said.

In his own Science article, Friedman writes that the overweight are fighting "a battle against biology" because obesity arises from a complex interplay of genetics and the environment.

Scientists have discovered a number of hormones and genes that generate a basic biological drive to eat that can be difficult to fight, he explains.

Scientists also know that the more volume and variety of food that people are offered — think super-sized restaurant portions and buffets — the more they will overeat, says CDC nutrition chief Dr. William Dietz.

"Portion size is an issue. How one goes about controlling it is not so simple," he cautions.

For people reluctant to eat less, Colorado's Hill points to a current experiment in which Colorado is encouraging people to buy $20 battery-operated step-counters and take an extra 2,000 steps a day, enough to walk a mile and burn 100 calories.

Hill is studying 500 participants to see if that extra little bit helps their weight; results are not due for another year or two. He plans to add his theory on eating 100 fewer calories to the study, too.

Copyright 2005 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.